Unless otherwise indicated herein, the description in this section is not prior art to the claims in this application and is not admitted to be prior art by inclusion in this section.
Generally, a typical tandem type image forming apparatus includes a plurality of photoreceptors and a plurality of developing units. The plurality of developing units develop respective plurality of electrostatic latent images on the photoreceptors as black toner images and a plurality of other colored toner images.
The toner images on the plurality of photoreceptors are transferred on an intermediate transfer belt, and furthermore, the toner images on the intermediate transfer belt are transferred on a sheet. The plurality of colored toner images are toner images of three colors of cyan, magenta, and yellow.
The plurality of developing units each include rotating units such as a developing roller and a stirring unit that stirs a toner. In the image forming apparatus, when image formations are performed in a color mode, every rotating unit of the developing units is driven.
On the other hand, it has been known that, when the image formations are performed in a monochrome mode, the rotating units are halted in the three developing units that perform the development of the colored toner images for preventing a deterioration of the toner.